Abstract

The authors report the impact response of water droplets impinging on superhydrophobiccarbon nanotube arrays and observe that arrays with different wetting properties display significantly different responses. For an array with a static contact angle of 163°, the droplet bounces off the surface several times, while for an array with a reduced contact angle of 140°, the droplet does not rebound and remains pinned. The contact angle hysteresis and contact line pinning for the 140° array suggest that the momentum of the droplet during the initial impact enables it to penetrate and displace the air pockets that are responsible for the superhydrophobicity of the array under static conditions.

Received 04 May 2007Accepted 15 June 2007Published online 09 July 2007

Acknowledgments:

The authors thank Pulickel Ajayan and Lijie Ci at RPI for providing the nanotube samples used in this research. They are also grateful to a reviewer for his/her comments which improved this manuscript. This work was supported in part by NSF under Award No. 0403789 (to N.K.).